title: Insulin secretion enhancing activity of roselle calyx extract in normal and streptozotocin-induced diabetic rats.
abstract: OBJECTIVE
  Our recent study revealed the antihyperglycemic activity of an ethanolic extract of roselle calyxes (Hibiscus sabdariffa) in diabetic rats. The present study had, therefore, an objective to investigate the mechanism underlying this activity.
  
  
  METHODS
  Male Sprague Dawley rats were induced to be diabetes by intraperitoneal injection of 45 mg/kg streptozotocin (STZ). Normal rats as well as diabetic rats were administered with the ethanolic extract of H. sabdariffa calyxes (HS-EE) at 0.1 and 1.0 g/kg/day, respectively, for 6 weeks. Then, blood glucose and insulin levels, at basal and glucose-stimulated secretions, were measured. The pancreas was dissected to examine histologically.
  
  
  RESULTS
  HS-EE 1.0 g/kg/day significantly decreased the blood glucose level by 38 ± 12% in diabetic rats but not in normal rats. In normal rats, treatment with 1.0 g/kg HS-EE increased the basal insulin level significantly as compared with control normal rats (1.28 ± 0.25 and 0.55 ± 0.05 ng/ml, respectively). Interestingly, diabetic rats treated with 1.0 g/kg HS-EE also showed a significant increase in basal insulin level as compared with the control diabetic rats (0.30 ± 0.05 and 0.15 ± 0.01 ng/ml, respectively). Concerning microscopic histological examination, HS-EE 1.0 g/kg significantly increased the number of islets of Langerhans in both normal rats (1.2 ± 0.1 and 2.0 ± 0.1 islet number/10 low-power fields (LPF) for control and HS-EE treated group, respectively) and diabetic rats (1.0 ± 0.3 and 3.9 ± 0.6 islet number/10 LPF for control and HS-EE treated group, respectively).
  
  
  CONCLUSIONS
  The antidiabetic activity of HS-EE may be partially mediated via the stimulating effect on insulin secretion.
authors.affiliation: Department of Pharmacology, Khon Kaen University, Khon Kaen, Thailand.
authors.forename: Eamruthai
authors.initials: E
authors.lastname: Wisetmuen
authors.forename: Patchareewan
authors.initials: P
authors.lastname: Pannangpetch
authors.forename: Bunkerd
authors.initials: B
authors.lastname: Kongyingyoes
authors.forename: Upa
authors.initials: U
authors.lastname: Kukongviriyapan
authors.forename: Wiboonchai
authors.initials: W
authors.lastname: Yutanawiboonchai
authors.forename: Arunporn
authors.initials: A
authors.lastname: Itharat
keywords: Antihyperglycemic activity; insulin secretion; pancreas; roselle